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Virus VS Worm

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Virus VS Worm

by karthikpandian19 » Mon Dec 26, 2011 3:29 am
All 250 files on Sam's hard drive are infected by either a virus or a worm or both. The number of files that are infected only by a worm is 2.5 times the number of files that are infected by both a virus and a worm. If 50% of the files were not infected by a virus, how many of Sam's files were NOT infected by a worm?

50
70
75
100
125
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by rijul007 » Mon Dec 26, 2011 4:24 am
karthikpandian19 wrote:All 250 files on Sam's hard drive are infected by either a virus or a worm or both. The number of files that are infected only by a worm is 2.5 times the number of files that are infected by both a virus and a worm. If 50% of the files were not infected by a virus, how many of Sam's files were NOT infected by a worm?

50
70
75
100
125



Image


Let No of files affected by both Virus and worm be x
No of files affected by worm only = 2.5 x

If 50% of the files were not infected by a virus
2.5x = 250/2
2.5x = 125
x = 50
how many of Sam's files were NOT infected by a worm?
y + x + 2.5x = 250
y + 50 + 125 = 250
y = 250 - 175 = 75

Option C
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by karthikpandian19 » Mon Dec 26, 2011 4:48 am
I am bit confused on this subject / explanation.

Can you explain please???
rijul007 wrote:
karthikpandian19 wrote:All 250 files on Sam's hard drive are infected by either a virus or a worm or both. The number of files that are infected only by a worm is 2.5 times the number of files that are infected by both a virus and a worm. If 50% of the files were not infected by a virus, how many of Sam's files were NOT infected by a worm?

50
70
75
100
125



Image


Let No of files affected by both Virus and worm be x
No of files affected by worm only = 2.5 x

If 50% of the files were not infected by a virus
2.5x = 250/2
2.5x = 125
x = 50
how many of Sam's files were NOT infected by a worm?
y + x + 2.5x = 250
y + 50 + 125 = 250
y = 250 - 175 = 75

Option C
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by rijul007 » Mon Dec 26, 2011 4:56 am
Heres another explaination

Lets say
number of files affected by Virus only = A
number of files affected by Worms only = B
Affected by both = C

A + B + C = 250
The number of files that are infected only by a worm is 2.5 times the number of files that are infected by both a virus and a worm.
B = 2.5C
If 50% of the files were not infected by a virus,
This means 50% are affected by worms only = B = 250/2 = 125
how many of Sam's files were NOT infected by a worm?
You are asked to find the number of files affected by Virus ONLY = A = 250 - (B+C) = 250 - (125 + 50 ) = 75
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by karthikpandian19 » Mon Dec 26, 2011 5:04 am
Thank you....now got it...
rijul007 wrote:Heres another explaination

Lets say
number of files affected by Virus only = A
number of files affected by Worms only = B
Affected by both = C

A + B + C = 250
The number of files that are infected only by a worm is 2.5 times the number of files that are infected by both a virus and a worm.
B = 2.5C
If 50% of the files were not infected by a virus,
This means 50% are affected by worms only = B = 250/2 = 125
how many of Sam's files were NOT infected by a worm?
You are asked to find the number of files affected by Virus ONLY = A = 250 - (B+C) = 250 - (125 + 50 ) = 75
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by karthikpandian19 » Tue Dec 27, 2011 9:45 pm
OA is 75
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